Inner spline member and manufacturing method thereof

ABSTRACT

An interior splined member is a hollow cylinder with an interior cylindrical surface defining a through hole. A major portion of the axial length of the interior cylindrical surface is splined to provide alternating axially extending ribs and troughs disposed between the ribs. A ring-shaped residual portion is an unsplined portion, i.e., a minor portion of the axial length of the interior cylindrical surface and is substantially circular with a diameter that is equal to or smaller than that of a circle on which the distal ends (tips) of the ribs lie. The trough portions are open at one end of the cylindrical member, while closed by the ring-shaped residual portion at the other end of the cylindrical member.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims, under 35 USC 119, priority of Japanese Application No. 2002-190385 filed on Jun. 28, 2002.

INCORPORATION BY REFERENCE

[0002] The disclosure of Japanese Patent Application No. 2002-190385 filed on Jun. 28, 2002 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

[0003] 1. Field of the Invention

[0004] The present invention relates to spline structure on an inner surface of a cylindrical element, and a manufacturing method thereof.

[0005] 2. Related Art

[0006] Cylindrical elements having a splined inner surface are widely used in, for example, automotive parts and the like. The splined inner surface of a cylindrical element is usually formed by broaching, which is a type of cutting, the interior surface of the cylindrical element.

[0007] However, manufacturing cylindrical elements with interior splines by conventional broaching encounters a number of problems. The tools for broaching are extremely costly and the process is very time consuming. Therefore, reducing the cost of forming the splines is difficult. In addition, broaching forms grooves by moving a tool in one axial direction and, therefore, burrs can be created on the edges of the grooves when the tool is removed. In such cases, a deburring process is necessary, further increasing the cost of the process.

[0008] The splines may also be formed by a cold forging process. However, by forming a splined portion through cold forging, burrs are created on edges thereof. Therefore, in this case as well, a deburring process becomes necessary, increasing the cost of the process.

[0009] Furthermore, when the deburring process is performed by cutting, the cutting is interrupted as the cutting tip alternately passes through the crests and through open areas of the splined surface and, therefore, the life of the cutting tip is extremely shortened.

SUMMARY OF THE INVENTION

[0010] In view of the foregoing problems, it is an object of the present invention to provide a cylindrical element with an interior splined surface and a method for manufacturing same which does not necessitate deburring and therefore is capable of reducing processing costs.

[0011] According to a first aspect of the present invention, a cylindrical member having a cylindrical interior surface defining a through hole, has its interior surface splined with alternating ribs (spline teeth) and troughs (grooves disposed between the ribs) extending axially over a major portion of the axial length of the cylindrical interior surface, from one end face at one end of the cylindrical member to a point on the cylindrical surface, with a minor portion (“ring-shaped portion”) of the interior surface, extending axially from that point to a second end face of the cylindrical member, opposite the one face, unsplined. The ring-shaped minor portion of the cylindrical surface is substantially circular with a diameter that is equal to or smaller than that of a circle defined by distal ends (tips) of the ribs. Thus, the troughs extend axially between ends, which are open at one end face of the cylindrical member, and opposite ends closed by the ring-shaped (“residual thickness”) portion.

[0012] As used herein “cylindrical member” is intended to include elements which are cylindrical overall, as well as elements having a cylindrical portion.

[0013] As described above, the interior splined member according to the present invention has a cylindrical interior surface including a splined portion and the ring-shaped residual portion. Further, the troughs of the splined portion are closed at one end by the ring-shaped residual (unsplined) portion. Thus, the troughs of the splined portion are closed at one end, instead of opening at both end faces of the cylindrical member (or “cylindrical portion”).

[0014] In manufacturing such a splined structure, a process for opening the trough portions at the closed end is not necessary and, therefore, the occurrence of burrs there is avoided, deburring is unnecessary and manufacturing costs can be reduced.

[0015] According to a second aspect of the present invention, a method for manufacturing an interior splined member includes the steps of:

[0016] providing a cylindrical member having a cylindrical interior surface defining a through hole,

[0017] forming splines on a portion of the cylindrical interior surface, the spined interior surface portion having alternating ribs (spline teeth) and troughs, disposed between the ribs, extending axially along the cylindrical interior surface, by cold forging of the cylindrical member, and

[0018] leaving unsplined a ring-shaped residual (minor axial length) portion having an inner surface that is substantially circular with a diameter that is equal to or smaller than a circle defined by distal ends (tips) of the ribs.

[0019] In the manufacturing method according to the present invention, the splined portion is formed by cold forging. More specifically, the cold forging process is performed such that the troughs are closed on the one end side by the ring-shaped residual portion, instead of the troughs of the splined surface penetrating both end faces of the cylindrical member.

[0020] Thus, when forming the splined portion by cold forging, the occurrence of burrs at end portions is reliably prevented. Therefore, processing costs can be reduced because a deburring process is not necessary.

[0021] The interior splined member according to the first aspect of the present invention preferably has the end face surfaces of the cylindrical member finished by cutting.

[0022] As described above, in the present invention, because a ring-shaped residual portion is left unsplined, when cutting the axial end face of the cylindrical member, at the side of the ring-shaped residual portion, continuous and smooth cutting can be performed, as contrasted with intermittent cutting. Further, the useful life of the cutting tip is thereby prolonged. Thus, the presence of the ring-shaped residual portion is particularly effective when cutting edge surfaces.

[0023] In addition, the edge surface of the ring-shaped residual portion is finished by cutting and, therefore, a ring shape without unevenness or a gear shape is obtained. Thus, for example, when used as a datum plane for a bearing, better stabilization of the state of contact with the bearing is realized, and the function of the interior splined member is improved.

[0024] Preferably, the method for manufacturing an interior splined member according to the second aspect of the present invention further includes finishing surfaces of the splines by cutting. In this case as well, smooth processing can be performed, and an interior splined member can be obtained with a greatly improved function.

[0025] In the method for manufacturing an interior splined member according to the second aspect of the present invention, the cold forging preferably includes using an outer peripheral punch (“ring”) supporting a cylindrical member around its outer peripheral surface, an end portion punch supporting one end portion of the cylindrical member, and a spline punch having a spline-forming portion, with a shape corresponding to that of the splined portion, and a column-forming portion with an outer diameter corresponding to the inner diameter of the ring-shaped residual portion. The ring-shaped residual portion is formed by supporting the cylindrical member with the outer peripheral punch and the end portion punch. The spline punch is inserted into the through-hole of the cylindrical member and moved along its interior surface to cut the splines. The spline punch is stopped at a position within the cylindrical member by abutment of the column-forming portion of the spline punch.

[0026] By performing cold forging utilizing at least the outer peripheral punch, the end portion punch, and the spline punch, the cylindrical member can be easily splined.

[0027] Provision of a brim-shaped flange portion on an end of the cylindrical member allows it to be utilized as a carrier cover, which is a part of the planetary gear set of an automatic transmission, and as elements for various other applications.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028]FIG. 1 is a partial cutout cross-sectional view of an interior splined member according to a first embodiment of the invention;

[0029]FIG. 2 is an explanatory drawing showing a blank cylindrical member set between an end punch and a ring member (“outer peripheral punch”) for executing a cold forging splining process according to the invention;

[0030]FIG. 3 is an explanatory drawing showing a state immediately after cold forging of the splines with the spline punch advanced within the cylindrical member according to the first embodiment;

[0031]FIG. 4 is an explanatory drawing showing a state in which an interior splined member is knocked out after completion of the cold forging process according to the first embodiment;

[0032]FIG. 5 is an explanatory drawing showing the shape of a cross-section of the interior splined member after completion of the cold forging process according to the first embodiment;

[0033]FIG. 6 is an explanatory drawing showing the shape of a cross-section of the interior splined member after cutting according to the first embodiment; and

[0034]FIG. 7 is a diagram showing the interior splined member as incorporated into a planetary gear set.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] A preferred embodiment of the present invention will now be described with reference to FIGS. 1 to 6.

[0036] As shown in FIG. 1, an interior splined member 1 of the present embodiment includes a cylindrical portion 2 providing a through hole 29, and a splined portion 20 providing alternating ribs 21 and troughs 22 disposed between the ribs (crests) 21 which extend axially along the inner surface of the cylindrical portion 2.

[0037] A ring-shaped residual thickness portion 23 has an inner peripheral surface that is substantially circular with a diameter identical to that of a circle defined by the distal tips (“crests”) of ribs 21. The troughs 22 are open at one end 202 and closed by the ring portion 23 at their other end 201.

[0038] As shown in FIG. 1, the interior splined member is a carrier cover for a planetary gear unit of an automatic transmission, including the cylindrical portion 2 and a brim-shaped flange portion 19 provided around the one end 201 of the cylindrical portion 2.

[0039] This interior splined member 1, as shown in FIG. 2, is formed from a starting piece (blank) 100 of a material such as steel (SAPH440) that includes the cylindrical portion 2, which provides the through hole 29 and which includes the flange portion 19.

[0040] Further, by cold forging of the interior surface of the cylindrical portion 2 of starting piece 100, the splines 20 are formed, with ring-shaped portion 23 left at the one end 201 of the cylindrical portion 2.

[0041] More specifically, as shown in FIGS. 2 to 5, the splined surface 20 is formed by use of an outer ring (“outer peripheral punch”) 51 supporting the cylindrical portion 2 in cooperation with an end portion punch 52 and a spline punch 53. The spline punch 53 includes a spline-forming portion 531 having a shape that corresponds to that of the splined surface 20 and a column-forming portion 532 with an outer diameter corresponding to that of the inner diameter of the ring portion 23. As further shown in FIG. 2, the cylindrical portion 2 is supported by holding the starting piece 100 between the ring 51 and the end portion punch 52.

[0042] Next, as shown in FIG. 3, the spline punch 53 is advanced relative to the inner surface of the cylindrical portion 2. A shoulder on the column-forming portion 532 of the spline punch 53 stops advance of the spline punch 53 at a position within the cylindrical portion predetermined to leave ring portion 23 without the cold-forged splines.

[0043] Thus, the starting piece 100 is formed into the interior splined member 1 having a splined surface portion 20 within the cylindrical portion 2 and a ring-shaped residual thickness portion 23.

[0044] Thereafter, as shown in FIG. 4, the interior splined member 1 is removed by retracting the end portion punch 52, and advancing a knock-out member 54 disposed between the ring 51 and the spline punch 53.

[0045] As shown in FIG. 5, the resultant cold-forged product is interior splined member 1 having excess material portions 251 and 252 respectively protruding axially from the one end portion 201 and the other end portion 202 of the cylindrical portion 2. Naturally, there are applications compatible with these excess material portions 251 and 252 left as is, but in the present embodiment, these excess material portions 251 and 252 are respectively removed by cutting. Thus, as shown in FIG. 6, an edge surface 261 is cut on an axial end of the ring-shaped residual portion, i.e., at the end 201 of the cylindrical portion 2. Furthermore, an edge surface 262 is cut on the opposite axial end 202 of the cylindrical portion 2 as well. Both of edge surfaces 261 and 262 are flat surfaces perpendicular to the axis of the cylindrical portion 2.

[0046] In the present embodiment, a cold forging process which forms the splines by the relative movement of the spline punch 53, does not form burrs on the end portion 202 of the cylinder 2 because the spline punch 53 is advanced from that end. In addition, on the end 201 side, the column-forming portion 532 of the spline punch 53 stops the relative forward advancement of the spline punch 53 at a position within the cylindrical portion 2, leaving the ring-shaped residual portion 23 unsplined, and formation of burrs is also avoided at the end 201 side. Accordingly, in the present embodiment, a deburring process is not necessary after forming the splines by cold forging, which reduces processing costs.

[0047] As described above, the interior splined member 1 of the present embodiment is a carrier cover for a planetary gear set and, therefore, it is necessary to provide highly accurate cut edge surfaces 261 and 262 on both end faces of the cylindrical portion 2 as described above.

[0048] In particular, the ring-shaped residual portion 23 is provided at the one end 201 of the cylindrical portion 2 and, therefore, the cutting of the edge surface 261 can be smoothly and continuously performed without intermittent cutting. Thus, it is also possible to avoid shortening of the life of the cutting tip used for this cutting. In addition, as described later, when using the cut edge surface 261 as a datum plane for a bearing, better stabilization of the contact with the bearing is achieved.

[0049] Thus, according to this preferred embodiment, it is possible to provide the interior splined member 1 and a manufacturing method therefor which do not require deburring and which reduce processing costs.

[0050]FIG. 7 illustrates the interior splined member 1 of the above-described preferred embodiment incorporated into a planetary gear unit 8.

[0051] In the planetary gear unit 8, as shown in FIG. 7, the interior splined member 1 is a carrier cover provided within the open end of a flange 84 of a hollow shaft 8 via an input sleeve 85. The cut edge surface 261 at the one end 201 of the cylindrical portion 2 of the interior splined member 1 functions as a datum plane on which a bearing 82 is disposed.

[0052] In addition, while other members such as a pinion shaft 83 and a carrier 84 are engaged with the interior splined member 1, the interior splined member 1 is engaged with the input sleeve 85 by splines. For this purpose, a splined portion 850 is formed on an outer peripheral surface of the input sleeve 85, and this is engaged with the splined portion 20 on the interior surface of the cylindrical portion 2 of the interior splined member 1.

[0053] As shown in FIG. 6 described earlier, the ring-shaped residual portion (original thickness portion) 23 described above closes the troughs 22 at the end 201 side of the cylindrical portion 2 of the splined member 1; however, the troughs 22 are open at the other end 202. Further, a sufficient length is secured for the splined portion 20. Thus, the engagement of the splined portion 850 of the input sleeve 85 with the splined portion 20 of the interior splined member 1 can be realized without any problems.

[0054] Further, as described above, in the planetary gear unit 8, a deburring process is unnecessary because the ring-shaped residual portion 23 is left unsplined and a reduction in the processing cost of the entire planetary gear unit is thereby achieved. In addition, since the cut edge surface 261 of the interior splined member 1 is formed as an edge surface of the ring-shaped residual portion 23, a smooth ring shape or gear shape is obtained, and its precision as a datum plane for a bearing is increased.

[0055] The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. 

What is claimed is:
 1. An interior splined member comprising a hollow cylindrical member having an interior cylindrical surface defining a through hole, said interior cylindrical surface including a splined portion providing alternating axially extending ribs and troughs and an unsplined ring-shaped residual portion that is substantially circular with a diameter equal to or smaller than the diameter of a circle defined by the distal ends of said ribs, said troughs opening at an end face at one axial end of said hollow cylindrical member and closed by said ring-shaped residual portion at a second axial end of said hollow cylindrical member.
 2. The interior splined member according to claim 1, wherein a cut edge surface is provided at the second axial end of the hollow cylindrical member.
 3. The interior splined member according to claim 1 wherein said splined portion extends over a major portion of the axial length of said interior cylindrical surface and said unsplined portion extends over a minor portion of the axial length of said interior cylindrical surface.
 4. A method for manufacturing an interior splined member comprising the steps of: providing a cylindrical member having an interior cylindrical surface defining a through hole; cold forming the interior cylindrical surface to form a splined portion on said interior cylindrical surface, said splined portion providing alternating, axially extending ribs and troughs; and leaving unsplined a ring-shaped residual portion of said interior cylindrical surface which is substantially circular with a diameter equal to or smaller than the diameter of a circle defined by distal ends of the ribs.
 5. The method for manufacturing an interior splined member according to claim 4, further comprising the step of: cutting an end face of the cylindrical member.
 6. The method for manufacturing an interior splined member according to claim 4, wherein the cold forging includes: supporting the cylindrical member around an outer peripheral surface using an outer peripheral punch; inserting an end portion punch into one end of the cylindrical member; inserting a spline punch into an end of the cylindrical member opposite the one end, the spline punch having a spline-forming portion with a shape corresponding to the spline portion and a column-forming portion with an outer diameter corresponding to an inner diameter of the ring-shaped residual portion; moving the spline punch relative to the interior cylindrical surface to form the splined portion; and stopping said moving of the spline punch at a position within the cylindrical member by abutment of at least one portion of the column-forming portion of the spline punch.
 7. The method for manufacturing an interior splined member according to claim 5, wherein the cold forging includes: supporting the cylindrical member around an outer peripheral surface using an outer peripheral punch; inserting an end portion punch into one end of the cylindrical member; inserting a spline punch into an end of the cylindrical member opposite the one end, the spline punch having a spline-forming portion with a shape corresponding to the spline portion and a column-forming portion with an outer diameter corresponding to an inner diameter of the ring-shaped residual portion; moving the spline punch relative to the interior cylindrical surface to form the splined portion; and stopping said moving of the spline punch at a position within the cylindrical member by abutment of at least one portion of the column-forming portion of the spline punch. 